Dozens of vehicles were abandoned and hundreds of others turned onto side roads to get away from the flames as water-dropping helicopters flew over the Cajon Pass area about 55 miles northeast of Los Angeles.

It’s not uncommon to see open, undeveloped land around the city. For one reason or another, the owner decides not to build. But those lots can turn into dry, open fields and fuel for a fire like the one that hit Sunday.

A fire in the Southern California mountains that threatens thousands of buildings was 40 percent contained on Friday — double the previous figure — as cooler weather helped slow the spread of the blaze.